Improvement in sliding slates for computation-cards



UNITED. STATES PATENT OFFICE,

GEORGE N. JACKSON, OF CHICAGO,` ILLINOIS.

Specification forming` part of Letters Patent No. 56,943, dated August 7, 18663 To all whom it may concern:

Be it known that I, GEORGE N. JACKSON, of Chicago, in the county of Cook and State of Illinois, have invented a Sliding Slate for ComputationCards; and I do hereby declare that the following, taken in connection with the drawing which accompanies and forms part of this specification, is a description of myinvention sufficient to enable those skilled in the art to practice it. 1

In teaching the fundamental rules of arithmetic tabular cards are sometimes employed, having numbers arranged in lines, columns, and divisions, in such manner that examples may be given to the student for all kinds of arithmctical practice without the necessity of copying the figures, the process of computation being worked out upon a slate.

In the use of such tables, however, it is often found troublesome to keep in view those, and only those, numbers entering into the example to be solved. and it is also somewhat difficult to perform the mental operations by the table while transferring the result to another card or slate.

To obviate these difficulties I haveW sought to devise some method which should combine the advantages of the arrangements of numbers printed upon the card with some means of forming a boundary-line to the particular examples to be solved and with a slate or blank surface combined directly with the card, and forming a base for working out the solutions. It is to such an arrangement that this invention relates, the invention consisting, in fact, of the combination, with a table having columns, lines, and divisions of fixed or permanent numbers, of a slate or computing surface arranged to slide vertically over the face oil the card, and so as to be retained in position as circumstances may require.

AThe drawing represents a tabular card embodyin g the invention, A showing a front face view, and B a cross-section, of it.

The vertical series of numbers are indicated by the successive numerals 1, 2, 3, Ste., at the top and bottom of the table, and the horizontal series by the capital letters A, B, C, Ste., at the opposite sides thereof, the vertical series being subdivided by vertical lines.

Across the face of the table is a slate or computing card or surface, a, the opposite with the operation to be performed, the upper edge of the slate defining the line above which are the figures entering into the example to be solved, and the surface of the slate being in theexact position required for working out the arithmetical process. For instance, suppose, in thevertical columns marked 1, 2, and

3, the figures between the lines marked C and J, inclusive, are to be added. The slate is slid up until the upper edge reaches the J and the computing-surface'is in position for the process, as-seen at A.

I claiml The combination, With the tabular card, of a computing-slate arranged to slide thereupon, substantially as set forth.

eno. N. Jackson.'

Witnesses G. W. WHEELER, WM. O. BALCK, 

